U.S. patent number 5,470,200 [Application Number 08/175,356] was granted by the patent office on 1995-11-28 for guide vanes for axial fans.
This patent grant is currently assigned to ABB Flakt Aktiebolag. Invention is credited to Borje Nilsson, Patrick Nilsson, Vladimir Tupov.
United States Patent |
5,470,200 |
Tupov , et al. |
November 28, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Guide vanes for axial fans
Abstract
A guide vane arrangement for axial fans, intended to translate
the rotational component of the gas flow velocity after passage
through the impeller (1) into a substantially axial velocity,
including a ring (2) of guide vanes disposed downstream of the fan
and in spaced relationship therewith. Alternate guide vanes are
axially displaced with respect to the remaining ones, so that
alternate guide vanes are at a first axial distance from the fan
and the remainder are at a second axial distance from the fan. As
an alternative, alternate guide vanes have a portion of the end
part facing towards the fan removed, so that the forward edge of
alternate guide vanes is at a first distance from the fan and the
remaining guide vanes are at a second axial distance, and the guide
vanes are non-uniformly distributed along the periphery of the
ring.
Inventors: |
Tupov; Vladimir (Moscow,
RU), Nilsson; Patrick (Vaxjo, SE), Nilsson;
Borje (Vaxjo, SE) |
Assignee: |
ABB Flakt Aktiebolag
(Stockholm, SE)
|
Family
ID: |
20383309 |
Appl.
No.: |
08/175,356 |
Filed: |
March 17, 1994 |
PCT
Filed: |
June 26, 1992 |
PCT No.: |
PCT/SE92/00481 |
371
Date: |
March 17, 1994 |
102(e)
Date: |
March 17, 1994 |
PCT
Pub. No.: |
WO93/01415 |
PCT
Pub. Date: |
January 21, 1993 |
Foreign Application Priority Data
Current U.S.
Class: |
415/195;
415/194 |
Current CPC
Class: |
F04D
29/661 (20130101); F04D 29/544 (20130101); F04D
29/666 (20130101) |
Current International
Class: |
F04D
29/40 (20060101); F04D 29/66 (20060101); F04D
29/54 (20060101); F01D 001/02 () |
Field of
Search: |
;415/208.2,209.1,211.2,220,210.1,194,195 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Look; Edward K.
Assistant Examiner: Sgantzos; Mark
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt
Claims
We claim:
1. Guide vane arrangement of axial fans, the arrangement
translating the rotational component of the gas flow velocity after
passage through the impeller (1) into a substantially axial
velocity, which comprises:
a ring (2) of guide vanes arranged downstream of the impeller and
in spaced relationship therewith, wherein alternate guide vanes
with an edge facing the impeller are axially displaced relative to
remaining guide vanes and wherein alternate guide vanes are located
a first axial distance from the fan and the remaining guide vanes
are located at a second axial distance from the fan, and the guide
vanes are non-uniformly distributed along a circumference of the
ring.
2. Arrangement according to claim 1, wherein a portion of an end
part facing towards the impeller (1) of the alternate guide vanes
is concave so that the forward edge of said guide vanes is at a
first axial distance from the fan and the remainder of the guide
vanes is at said second axial distance from the fan.
3. Arrangement as claimed in claim 2, wherein the alternate guide
vanes are out of alignment in the circumferential direction
relative the remaining guide vanes, with a constant displacement,
so that the distance in the circumferential direction between
adjacent guide vanes varies between two given values.
4. Arrangement as claimed in claims 1 or 2, wherein the axial
displacement between the alternate guide vanes and the remaining
guide vanes is in an interval of l/l.sub.ch =0.40-0.7 where l
denotes the magnitude of the displacement and l.sub.ch denotes the
length of the guide vane.
5. Arrangement as claimed in claim 2, wherein the angular
displacement in a circumferential direction has an interval of
5.degree.-15.degree..
6. Arrangement as claimed in claim 1, wherein the guide vane ring
(2) comprises first and second rings (20, 22) positioned axially in
tandem wherein said alternate guide vanes are carried by said first
rings and the remaining guide vanes by said second ring, and
wherein said first and second rings are mutually axially
displaceable and/or radially rotatable relative each other about a
common axis.
7. Arrangement as claimed in claim 1, wherein the guide vanes, in a
part facing towards the fan, are formed with a web between radially
outer and inner portions of the guide vanes, and wherein an arcuate
length at the level of the web is shorter than at said outer and
inner portions.
8. Arrangement as claimed in claim 1, wherein the number of guide
vanes is between 0.5 and 2.1 times the number of blades of the
impeller.
9. Arrangement as claimed in claim 4, wherein l/l.sub.ch =0.5.
10. Arrangement as claimed in claim 3, wherein the angular
displacement in the circumferential direction has an interval of
10.degree..
11. Arrangement as claimed in claim 4, wherein the angular
displacement in the circumferential direction has an interval of
10.degree..
Description
TECHNICAL FIELD
The following invention relates to a guide vane arrangement for
axial fans, intended to convert the rotational component in the gas
flow velocity after passage through the impeller into a
substantially axial velocity, the arrangement including a ring of
guide vanes disposed downstream of the fan and in spaced
relationship therewith.
BACKGROUND ART
The gas flow downstream of the impeller of an axial fan normally
rotates. The rotational energy can be translated into useful energy
by a guide vane arrangement on the outlet side of the fan, this
arrangement converting the rotational velocity to an axial velocity
component. The pressure is raised in this way, and the efficiency
of the fan increases. Normally, however, the sound level also
increases at the same time.
The sound from a fan comprises tonal components, i.e. tones with
discrete frequencies and a wide band noise with a continuous
frequency spectrum. Considerable efforts have been made primarily
to lower the tonal components, by a suitable arrangement and
embodiment of guide vanes on the output side of the fan.
It is accordingly a general understanding that the noise generated
decreases with increasing distance between the impeller and guide
vanes, see M. J. Benzakein, J. Acoust. Soc. Am. 51 (1972),
1427-1438 and W. Neise, Proc. INTER-NOISE 1988, pp 767-776. It has
been found, however, this is not always applicable.
A guide vane is described in the Swedish patent 8802136-5, which
has improved aerodynamic and acoustic properties.
It has also been found earlier that a non-uniform distribution of
the guide vanes in the ring of guide vanes can give rise to certain
acoustic improvements, although it has been found that large
deviations from a uniform distribution of the guide vanes give rise
to aerodynamic problems.
It is also known that certain acoustic characteristics can be
improved by a portion being cut out from alternate guide vanes in
their the forward portions.
FIG. 1 illustrates how the strength in an individual tone can be
reduced by displacing the guide vanes in the circumferential
direction of the guide vane ring. It will also be seen from the
same figure that the noise at higher frequencies over about 500 Hz
also increases at the same time. The measurement has been made for
a fan R.P.M. of n=970 and a displacement of alternate guide vanes
of .beta.=10.degree. and .beta.=0.degree..
DISCLOSURE OF THE INVENTION
The object of the present invention is to lower individual,
disturbing tones in the fan sound, as well as lower the general
noise level in a simple way.
The first-mentioned object is achieved with a guide vane ring of
the kind mentioned in the introduction, and with characteristics
disclosed hereinbelow 1.
The second object is achieved by a further development of the
inventive guide vane arrangement, in which alternate guide vanes
are axially displaced relative the remaining ones, so that
alternate guide vanes are at a first axial distance from the fan,
and the remainder at a second axial distance, simultaneously as the
guide vanes are non-uniformly distributed in the guide vane ring
circumference. Preferably, alternate guide vanes are displaced in
the circumferential direction relative to the remaining guide vanes
with a constant displacement so that the distance in the
circumferential direction between juxtaposed guide vanes alternates
between two given values. This arrangement reduces both individual
tones and the general wide band noise from the fan. In addition,
this combination of axial displacement and circumferential
displacement of the guide vanes provides improved efficiency of the
fan, compared with the case using a guide vane arrangement with
only axial displacement of the guide vanes, or only rotation of the
vanes in the circumferential direction.
By the combination of measures according to this further
development of the apparatus in accordance with the invention,
there are achieved highly important advantages, both with respect
to acoustics and efficiency, considerably exceeding the effects
achieved by the individual measures of axial displacement or
circumferential rotation of the guide vanes.
In accordance with another advantageous embodiment of the inventive
apparatus, the axial displacement of the guide vanes is in the
interval 0,4-0,7 l/l.sub.ch, preferably 0,5 l/l.sub.ch, where l
denotes the magnitude of the displacement and l.sub.ch the length
along the guide vane.
In accordance with yet another advantageous embodiment, the
displacement in the circumferential direction is in the interval
5.degree.-15.degree., and is preferably 10.degree..
In accordance with a further advantageous embodiment of the
apparatus in accordance with the invention, the guide vane ring
arrangement is divided into two rings axially in tandem, alternate
guide vanes being carried by one ring and the other guide vanes by
the other ring, the rings being axially displaceable relative to
each other or radially rotatable relative each other about a common
axis. It is thus possible to adjust the guide vane arrangement in a
simple way to achieve optimum conditions.
In accordance with a further advantageous embodiment of the
invention, in the portion facing towards the impeller the guide
vanes are designed with a web configuration between the radially
outer and inner portions of the guide vane such that the arcuate
length along the single-curved guide vane at the level of the web
is shorter than at said mentioned outer and inner portions.
BRIEF DESCRIPTION OF THE DRAWINGS
Emodiments of the arrangements in accordance with the invention,
selected as examples, will now be described in greater detail and
with reference to the accompanying drawings, wherein
FIG. 1 illustrates the effect on the sound level from the fan when
alternate guide vanes are displaced in the circumferential
direction in accordance with prior art;
FIG. 2 illustrates an axial fan with guide vanes arranged
downstream of the fan;
FIG. 3 schematically illustrates five different guide vane
arrangements which include: a) guide vanes arranged uniformly
according to the prior art, b) alternate guide vanes displaced in
the circumferential direction of the guide vane ring according to
the prior art, c) alternate guide vanes axially displaced in
accordance with the invention, d) a combination of axial
displacement and rotation of the guide vane ring in a
circumferential direction in accordance with the invention, e) the
combination of the displacement in the circumferential direction
and the provision of a cut-out in alternate guide vanes in
accordance with the invention;
FIG. 4 illustrates the effect on the sound from the fan resulting
from the axial displacement of the alternate guide vanes in
accordance with the operational case c) in FIG. 3;
FIG. 5 illustrates the effect on the sound level from the fan of
the combination of axial displacement and displacement of the guide
vanes in the circumferential direction of the guide vane ring
according to the operational case d) in FIG. 3
FIG. 6 illustrates the reduction of sound in the tone at the blade
frequency as a function of the rotation in the circumferential
direction for a given axial displacement of the guide vanes;
FIG. 7 illustrates an embodiment of the arrangement where two guide
vane rings are used and
FIG. 8 illustrates a particular guide vane configuration.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 illustrates an axial fan installed in a duct 4 and having a
guide vane ring 2 arranged in spaced relationship with, and
downstream of the impeller 1. The number of guide vanes is
preferably between 0.5 and 2.1 times the number of blades in the
impeller.
In FIG. 1 the effects on the sound from a fan with guide vane
arrangements according to the principles shown in FIGS. 3a and 3b
are compared under the conditions given above. It will be seen from
FIG. 1 that displacement Lw (dB) of alternate guide vanes in the
circumferential direction of the guide vane ring according to FIG.
3b results in a heavy decrease of a tone at the blade frequency f
(Hz) of 160 Hz, while there is an increase in the noise level for
frequencies over about 500 Hz.
FIG. 4 compares the effect on the sound level f (Hz) of the guide
vane arrangements according to FIGS. 3a and 3c. It will be seer
that there is a considerable lowering of the tone at the blade
frequency f (Hz) 160 Hz of about 3.5 dB, while there is an increase
o the wide band high frequency noise over about 500 Hz. The
operational conditions are the same as for FIG. 1.
In FIG. 5 the sound levels for the guide vane arrangements
according to FIGS. 3a and 3d are compared. A surprising result will
be seen from this figure in that the combination of axial
displacement and rotation (i.e., being out of alignment) in the
circumferential direction of the ring of alternate guide vanes
leads to a reduction of the sound level over the entire frequency
range, compared with a conventional guide vane arrangement with
uniformly distributed guide vanes. FIG. 5 demonstrates that both
discrete tones at lower frequencies and the wide band high
frequency noise are antenuated in an embodiment according to FIG.
3d. The axial displacement of the guide vanes is l/l.sub.ch =0,5,
where l denotes the magnitude of the displacement and l.sub.ch the
length along the guide vane, i.e. the displacement amounts to half
the length of the guide vane. Rotation in the circumferential
direction amounts to 10.degree.. The curves are measured for a fan
R.P.M. of n=970.
In FIG. 6 there is illustrated the attenuation .DELTA.L.sub.W at
the blade frequency, as a function of the rotation B of alternate
guide vanes in a guide vane arrangement where the alternate guide
vane is also axially diplaced by half the length of the guide vane.
The graphs are shown for two different revolutionary velocities of
the fan, namely n=970 rpm, and n=1430 rpm. This diagram shows that
a considerable reduction of tonal components is achieved in the
angle range 5.degree.-15.degree. for the axial displacement of the
guide vanes that is under consideration. Measurements have also
shown that some improvement in aerodynamic efficiency of the fan in
the region where the best sound attenuation is achieved.
Another acoustically advantageous embodiment of the apparatus
according to the invention is illustrated in FIG. 3e. In this
embodiment a portion of the end part facing towards the impeller of
alternate guide vanes is concave, so that the forward edge of these
guide vanes is at a first axial distance from the impeller and the
remainder at a second axial distance. In addition, the guide vanes
are non-uniformly distributed round the circumference of the
ring.
In FIG. 7 there is illustrated a further advantageous embodiment of
the guide vane ring 2 in the apparatus in accordance with the
invention. The ring 2 includes two rings 20,22 mounted on a common
shaft. Here, alternate guide vanes are carried by one of the two
rings and the other by the other ring. The two rings are mutually
axially displacable and relatively rotatable about the common
shaft. With this embodiment of the guide vane ring 2 there is
enabled in a simple way the axial displacement and rotation along
the circumference of the guide vanes relative each other so that
desired properties are achieved.
FIG. 8 illustrates an embodiment of a guide vane 6, which is found
to be advantageous in the arrangement according to the invention.
The end portion of the guide vane 10, which is intended to face
towards the impeller has an edge 10 with a parabola-like
configuration, so that between the inner and outer longitudinal
edges 12 and 14 of the guide vane 6 there is a web with a shorter
length L.sub.2 along the guide vane than said edges L.sub.1 and
L.sub.3, respectively. The guide vane has a straight back edge 16.
If the height of the web from the inner longitudinal edge 12 is
denoted by H.sub.1 and the total height of the guide vane by
H.sub.2 the position of the web is determined by the condition:
and preferably
* * * * *